Urethane resin compositions are used for various applications such as coating agents and adhesives since they generally have good adhesion to substrates and can form a soft coating.
One known urethane resin composition, for example, is a water-based polyurethane dispersion obtained by reacting a mixture containing a) at least one organic aliphatic, alicyclic, or aromatic di-, tri-, or polyisocyanate; b) at least one isocyanate-reactive polycarbonate diol, triol, or polyol; c) at least one compound having at least one isocyanate-reactive group and at least one unsaturated group polymerizable by free radicals; d) at least one compound having at least one isocyanate-reactive group and at least one dispersing group; and optionally e) at least one compound having at least two isocyanate-reactive groups and having a molecular weight of less than 1,000 g/mol, preferably less than 500 g/mol, and then dispersing the resulting reaction product in water (see, for example, PTL 1).
Research has been directed to the use of urethane resin compositions for applications such as surface coatings on optical components, including those for flexible displays. Unfortunately, a coating formed from the above water-based polyurethane dispersion has insufficient softness, e.g., insufficient elongation and flexibility, and may exhibit defects such as whitening when the coated article is bent. The coating formed from the above water-based polyurethane dispersion also has insufficient hardness and is susceptible to scratches, for example, when used as a surface coating on a touch panel, which may result in problems such as poor appearance.